This invention is related to an improved Analog to Digital Converter.
Analog to Digital Converters (ADC) are wellknown circuitries to convert an analog input voltage into a digital output signal as a number of bits. Normally there is a linear correlation between input voltage and digital output value.
Since several years so-called Delta-Sigma ADCs are known which use an oversampling approach to convert the input signal using integrators, comparetors and digital filters to convert the analog input signal into a digital output signal. Descripton of this kind of ADC and some embodiments can be found in:
(1) Delta-Sigma Data Converters: Theory, Design, and Simulation by Steven R. Norsworthy, a. o. ISBN: 0780310454 (1996)
The advantage of Delta-Sigma ADCs Is the insensitivity for some imperfections and tolerances of the analog part of the ADC.
Due to the German patent application (2) DE 195 18 508 A1 and the Japanese patent JP 10-2734731 B2 Delta-Sigma ADCs are known which are constructed only from two resistors and one integrator capacitor. Furthermore only a digital Integrated circuit is used. (FIG. 1)
To also achieve the conversion of small input voltages the peak-peak voltage at the input of the flipflop (FF) must remain in the magnitude of the construction related crosstalk and input noise voltages. Under construction related crosstalk and input noise voltages especially crosstalk from adjacent circutries and noise on the supply wires of the FF should is meant.
Because the supply voltage is used as reference voltage in simple Delta-Sigma ADCs the quality which means the resolution of the converter is direct correlated to the quality of the supply voltage. Without additional means this leads to a resolution of 7 bits of the ADC, what is also mentioned in (2).
The present invention shows means how to improve the analog part of a Delta Sigma ADC (analog frontend) so that by maintaining the simplicity of the construction a significant improvement of the resolution is achieved. Aimed at is a resolution of at least 13 bits because this is a must for commonly used audio codecs.